Methods and apparatus to enhance paper and board forming qualities

Abstract

Methods and apparatus to enhance paper and board forming qualities with insert tubes and/or a diffuser block in the paper forming machine headbox component which generates vorticity in the machine direction (MD) which is superimposed on the streamwise flow to generate a swirling or helical flow through the tubes of the diffuser block. Tubes of the diffuser block are designed such that the direction of the swirl or fluid rotation of the paper fiber stock may be controlled and the direction thereof is controlled in such a way to provide effective mixing, coalescence and merging of the jets of fluid emanating from the tubes into the converging section, i.e., nozzle chamber of the headbox. Also disclosed is the effective mixing of the jets generating cross-machine direction (CD) shear between the rows of jets that form at the outlet of the tubes inside the nozzle chamber of the headbox to align paper fibers in the cross-machine direction, thus increasing CD strength of the manufactured sheet. Vortex forming means are described for a plurality of tubular elements in the diffuser box for generating controlled axial vortices in the machine direction promoting mixing of the jets of paper stock from the tubular elements as the jets flow into the nozzle chamber to a uniform flow field of stock at the slice opening for the rectangular jet. Further embodiments, which include methods and apparatus for generating vorticity by pressure pulse devices and magnetically actuated finned bodies, are also described.

What is claimed is: 
     
       1. A paper forming machine headbox component for receiving a paper fiber stock and generating a jet therefrom for discharge upon a wire component moving in a machine direction (MD), the headbox component comprising: a distributer for distributing stock flowing into the headbox component in a cross-machine direction (CD), the distributer effective for supplying a flow of said stock across the width of the headbox in the machine direction;   a nozzle chamber having an upper surface and a lower surface converging to form a rectangular outlet lip defining a slice opening for the jet; and   a diffuser block coupling said distributer to said nozzle chamber, said diffuser block comprising:   a multiplicity of tubular elements disposed between said distributer and said nozzle chamber, said tubular elements being oriented axially in the machine direction, a plurality of the tubular elements having a longitudinal axes in the direction of the flow of stock, and the tubular elements arranged within the diffuser block as a matrix of rows and columns for generating multiple jets of said stock flowing into said nozzle chamber; and   at least one pressure pulse generating element mounted in or on each of said plurality of said tubular elements of said diffuser block, said pressure pulse generating element being effective for swirling said stock in controlled axial vortices around the longitudinal axes of the tubular elements as said stock flows through said tubular elements in the machine direction, each vortex being directed in a defined direction having a specific vorticity vector sign, defined as positive being in the machine direction or negative being opposite the machine direction based upon the right hand rule, said vortices promoting mixing of the jets of said stock as said jets flow into said nozzle chamber from the tubular elements to form a uniform flow of stock at the slice opening for the jet.   
     
     
       2. A paper forming machine headbox component as set forth in claim 1 wherein the number of pressure pulse generating elements mounted on or in said plurality of said tubular elements is from 2 to 12. 
     
     
       3. A paper forming machine headbox component as set forth in claim 1 wherein said pressure pulse generating elements are acoustic devices. 
     
     
       4. A paper forming machine headbox component as set forth in claim 1 wherein said pressure pulse generating elements are electromagnetic devices. 
     
     
       5. A paper forming machine headbox component as recited in claim 1 wherein said tubular elements comprise a flat section inlet for receiving said stock from said distributer and an elongated section outlet for directing the jets of said stock from said tubular elements as said jets flow into said nozzle chamber. 
     
     
       6. A paper forming machine headbox component as recited in claim 1 wherein said tubular elements comprise an insert tube insertable in said diffuser block for receiving said stock from said distributer. 
     
     
       7. A paper forming machine headbox component as recited in claim 1 wherein one row or column of tubes has a stock with controlled axial vortices having a specific vorticity vector sign which is positive and an adjacent row or column has a stock with controlled axial vortices having a specific vorticity vector sign which is negative. 
     
     
       8. A method of mixing jets of paper fiber stock flowing through and emanating from a multiplicity of tubes, the tubes having longitudinal axes extending substantially in the machine direction and in the direction of the flow of the stock, the tubes arranged as a matrix of rows and columns with the longitudinal axes of the tubes aligned in a diffuser block, the diffuser block and tubes coupled to a nozzle chamber in a paper forming machine headbox for discharging a uniform flow field of stock upon a wire component moving in a machine direction (MD), the method comprising: providing swirling jets of liquid paper fiber stock by means of a pressure pulse generating elements mounted in or on a plurality of tubes, the stock having controlled axial vorticity around the longitudinal axes of the tubes, the paper fiber stock emanating from the diffuser block substantially in the machine direction, each jet being directed in a defined direction about the longitudinal axes of each of said plurality of said tubes, said defined direction having a specific vorticity vector sign, defined as positive being in the machine direction or negative being opposite the machine direction based on the right-hand rule; and   positioning more than one of said tubes adjacent one another to mix said jets emanating from the tubes into the nozzle chamber.   
     
     
       9. A method as recited in claim 8 wherein said positioning step positions said positive jets of each of said plurality of said tubes adjacent one another in the diffuser block generating small scale turbulent flows in the nozzle chamber as the jets emanate from said tubes promoting mixing of said stock in the nozzle chamber. 
     
     
       10. A method as recited in claim 8 wherein said positioning step positions said positive jets along at least one of the rows of the matrix in the diffuser block generating a first secondary flow in the nozzle chamber in a cross-machine direction (CD), substantially perpendicular to the machine direction, as the row of positive jets emanate from the tubes. 
     
     
       11. A method as recited in claim 8 comprising the steps of: generating negative jets of paper fiber stock emanating from the diffuser block in controlled axial vortices in the machine direction for a second plurality of said tubes, the direction of each vortex being directed in a second negative-defined direction about the axes of each of said second plurality of said tubes; and   positioning at least one of said negative jets adjacent another one of said negative jets promoting mixing as said jets flow into the nozzle chamber.   
     
     
       12. A method as recited in claim 11 wherein said positioning step positions said positive jets of said first plurality of said tubes adjacent said negative jets of said second plurality of said tubes in the diffuser block promoting uniform flow of said stock emanating from said tubes into the nozzle chamber. 
     
     
       13. A method as recited in claim 11 wherein said positioning step positions said positive jets along at least one of the rows of the matrix in the diffuser block generating a first secondary flow in the nozzle chamber in a cross-machine direction (CD), substantially perpendicular to the machine direction, as the row of positive jets emanate from the tubes. 
     
     
       14. A method as recited in claim 13 wherein said positioning step positions said negative jets along at least another one of the rows of the matrix in the diffuser block generating a second secondary flow in the nozzle chamber in an opposite cross-machine direction as the row of negative jets emanate from the tubes. 
     
     
       15. A method as recited in claim 14 wherein said positioning step positions the row of negative jets adjacent the row of positive jets generating opposing secondary flows in the cross-machine direction as the rows of jets emanate from the tubes providing shear layers aligning the paper fibers of said stock in the cross-machine direction. 
     
     
       16. A method as recited in claim 8 wherein the number of pressure pulse generating elements mounted on or in said plurality of tubes is from 2 to 12. 
     
     
       17. A method as recited in claim 8 wherein said pressure pulse generating elements are acoustic devices. 
     
     
       18. A method as recited in claim 8 wherein said pressure pulse generating elements are electromagnetic devices. 
     
     
       19. A paper forming machine headbox component for receiving a paper fiber stock and generating a jet therefrom for discharge upon a wire component moving in a machine direction (MD), the headbox component comprising: a distributer for distributing stock flowing into the headbox component in a cross-machine direction (CD), the distributer effective for supplying a flow of said stock across the width of the headbox in the machine direction;   a nozzle chamber having an upper surface and a lower surface converging to form a rectangular outlet lip defining a slice opening for the jet; and   a diffuser block coupling said distributer to said nozzle chamber, said diffuser block comprising:   a multiplicity of tubular elements disposed between said distributer and said nozzle chamber, said tubular elements being oriented axially in the machine direction, a plurality of the tubular elements having a longitudinal axes in the direction of the flow of stock, and the tubular elements arranged within the diffuser block as a matrix of rows and columns for generating multiple jets of said stock flowing into said nozzle chamber; and   a body with at least two fins mounted within each of said plurality of said tubular elements of said diffuser block, at least three magnetic rings mounted around each of said plurality of said tubular elements, said magnetic rings being spaced along the length of said tubes in a position to coact with said finned body for swirling said stock in controlled axial vortices around the longitudinal axes of the tubular elements as said stock flows through said tubular elements in the machine direction, each vortex being directed in a defined direction having a specific vorticity vector sign, defined as positive being in the machine direction or negative being opposite the machine direction based upon the right hand rule, said vortices promoting mixing of the jets of said stock as said jets flow into said nozzle chamber from the tubular elements to form a uniform flow of stock at the slice opening for the jet.   
     
     
       20. A paper forming machine headbox component as set forth in claim 19 wherein the number of fins on said body is from 2 to 12. 
     
     
       21. A paper forming machine headbox component as set forth in claim 19 wherein said finned body has externally extending fins. 
     
     
       22. A paper forming machine headbox component as set forth in claim 19 wherein said finned body has internally extending fins. 
     
     
       23. A paper forming machine headbox component as recited in claim 19 wherein said tubular elements comprise a flat section inlet for receiving said stock from said distributer and an elongated section outlet for directing the jets of said stock from said tubular elements as said jets flow into said nozzle chamber. 
     
     
       24. A paper forming machine headbox component as recited in claim 19 wherein said tubular elements comprise an insert tube insertable in said diffuser block for receiving said stock from said distributer. 
     
     
       25. A paper forming machine headbox component as recited in claim 19 wherein one row or column of tubes has a stock with controlled axial vortices having a specific vorticity vector sign which is positive and an adjacent row or column has a stock with controlled axial vortices having a specific vorticity vector sign which is negative. 
     
     
       26. A method of mixing jets of paper fiber stock flowing through and emanating from a multiplicity of tubes, the tubes having longitudinal axes extending substantially in the machine direction and in the direction of the flow of the stock, the tubes arranged as a matrix of rows and columns with the longitudinal axes of the tubes aligned in a diffuser block, the diffuser block and tubes coupled to a nozzle chamber in a paper forming machine headbox for discharging a uniform flow field of stock upon a wire component moving in a machine direction (MD), the method comprising: providing swirling jets of liquid paper fiber stock by means of a body with at least two fins which is mounted in a plurality of tubes, the body being kept in circular motion by magnetic force, the stock having controlled axial vorticity around the longitudinal axes of the tubes, the paper fiber stock emanating from the diffuser block substantially in the machine direction, each jet being directed in a defined direction about the longitudinal axes of each of said plurality of said tubes, said defined direction having a specific vorticity vector sign, defined as positive being in the machine direction or negative being opposite the machine direction based on the right-hand rule; and   positioning more than one of said tubes adjacent one another to mix said jets emanating from the tubes into the nozzle chamber.   
     
     
       27. A method as recited in claim 26 wherein said positioning step positions said positive jets of each of said plurality of said tubes adjacent one another in the diffuser block generating small scale turbulent flows in the nozzle chamber as the jets emanate from said tubes promoting mixing of said stock in the nozzle chamber. 
     
     
       28. A method as recited in claim 26 wherein said positioning step positions said positive jets along at least one of the rows of the matrix in the diffuser block generating a first secondary flow in the nozzle chamber in a cross-machine direction (CD), substantially perpendicular to the machine direction, as the row of positive jets emanate from the tubes. 
     
     
       29. A method as recited in claim 26 comprising the steps of: generating negative jets of paper fiber stock emanating from the diffuser block in controlled axial vortices in the machine direction for a second plurality of said tubes, the direction of each vortex being directed in a second negative-defined direction about the axes of each of said second plurality of said tubes; and   positioning at least one of said negative jets adjacent another one of said negative jets promoting mixing as said jets flow into the nozzle chamber.   
     
     
       30. A method as recited in claim 29 wherein said positioning step positions said positive jets of said first plurality of said tubes adjacent said negative jets of said second plurality of said tubes in the diffuser block promoting uniform flow of said stock emanating from said tubes into the nozzle chamber. 
     
     
       31. A method as recited in claim 29 wherein said positioning step positions said positive jets along at least one of the rows of the matrix in the diffuser block generating a first secondary flow in the nozzle chamber in a cross-machine direction (CD), substantially perpendicular to the machine direction, as the row of positive jets emanate from the tubes. 
     
     
       32. A method as recited in claim 31 wherein said positioning step positions said negative jets along at least another one of the rows of the matrix in the diffuser block generating a second secondary flow in the nozzle chamber in an opposite cross-machine direction as the row of negative jets emanate from the tubes. 
     
     
       33. A method as recited in claim 32 wherein said positioning step positions the row of negative jets adjacent the row of positive jets generating opposing secondary flows in the cross-machine direction as the rows of jets emanate from the tubes providing shear layers aligning the paper fibers of said stock in the cross-machine direction. 
     
     
       34. A method as recited in claim 26 wherein the number of fins mounted on said body is from 2 to 12. 
     
     
       35. A method as recited in claim 26 wherein said body has externally extending fins. 
     
     
       36. A method as recited in claim 26 wherein said body has internally extending fins.